The invention relates to the generation of visually displayed repetitive patterns which may be used in the fields of visual, biological and psychological testing and in visual displays such as animated displays.
Bar patterns or gratings in particular have found increased acceptance in the field of visual testing since first proposed by O. H. Schade, in the article "Optical and Photoelectric Analog of the Eye" published in the Journal of the Optical Society of America, Vol. 46, pages 721-739 (1956). The December 1981 report "Proposed New Vision Standards for the 1980's and Beyond: Contrast Sensitivity", by Major Arthur Ginsburg of the Air Force Aeromedical Research Laboratory, for example, describes current state-of-the-art visual testing and contains several references to articles involving the use of sinusoid gratings.
The Ginsburg report also shows at page 7 several examples of sinusoid gratings which could have been generated using the present invention and shows a possible relation of these examples to aircraft pilot visual needs by way of a series of contrast varied photographs.
The Ginsburg report is published by the Air Force Aerospace Medical Research Laboratory of the Aerospace Medical Division of the Air Force Systems Command at Wright-Patterson AFB, Ohio 45433. This report received the technical review and approval identified as AFAMRL-TR-80-121. Copies of the report may be purchased from the National Technical Information Service at 5285 Port Royal Road, Springfield, VA 22161 or, for use by Federal Government agencies and their contractors from the Defence Documentation Center, Cameron Station, Alexandria, VA 22314.
The Ginsburg report also shows, on page 10, a correlation between sinusoidal gratings of various frequency and subtended visual angle and the information needed by a human subject to recognize two alphabet letters commonly used in the Snellen visual acuity measurement chart. As is pointed out by Major Ginsburg, many of the past practices in visual measurement have been notably lacking in completeness in areas addressed by the sinusoids or other bar patterns generated with the present invention.
Sinusoidal intensity gratings have also been found useful in the field of psycological testing where a tested subject's response to confusion, frustration, blurred images, and discomforting image movement are evaluated.
The patent art contains examples of electrically generated patterns; this art includes the U.S. Pat. No. 4,707,710 of J. S. Sukonick which discloses a raster scan computer graphic apparatus that includes split screen and zoom display features and permits the display of information stored in a memory. The Sukonick patent also teaches the display of multiple images of the same object at different magnification, the incorporation of alpha/numeric messages in the display and the ability to move portions of an image to a new display location. FIG. 2d of the Sukonick patent shows a greatly magnified image of a bar-like pattern together with the related video signal--which indicates the displayed bars are intended to be trapezoidal or square wave in nature.
The patent of P. M. Murray U.S. Pat. No. 4,119,956 shows a raster scan display apparatus for computer generated images in which the displayed image is filtered or smoothed according to the sum of the video signals for each line. This smoothing achieves an image having graded intensity changes that are more nearly analog in nature than would result from digital processing systems.
The U.S. Pat. No. 4,370,733 of J. J. Gaudio, shows a display apparatus wherein the displayed signal is developed from the summation of two preexisting display signals. The intensity of the displayed signal in the Gaudio patent is controlled by way of predetermined fractions of the periodic waveform which energizes the display. The preferred embodiment of the Gaudio invention employs electric lamp bulbs of three complementing colors to compose an element of the displayed image.
The U.S. Pat. No. 4,225,861 of G. G. Langdon et al, discloses an apparatus and method for artificially supplying texture or roughness to a displayed image by changing the color composition of the image using image processing apparatus.
The U.S. Pat. No. 4,200,869 of Murayama et al, discloses a digital display apparatus employing refresh memory storage of the displayed information and disclosing the ability to shift a displayed image. The Murayama et al apparatus contemplates the use of a display control bit to determine whether particular memory words are to be displayed on the screen. Murayama et al also contemplate the scrolling up or down of a displayed image at a controllable scrolling rate determined by hardware or an external instruction.
The above mentioned Arthur Ginsburg also has a U.S. Pat. No. 4,365,873 for a "Spatial Frequency and Contrast Sensitivity Test Chart", this document relates to the above mentioned AFAMRL-TR-80-121 report concerning vision standards. The Ginsburg patent includes a figure showing examples of sinewave gratings with low, medium and high spatial frequencies at low and high contrast and also includes definitions of spatial frequency and contrast. The Ginsburg patent and report are hereby incorporated by reference herein.
Two other Department of the Air Force employees, Henning E. von Gierke and Adolf R. Marko also have a U.S. Pat. No. 4,511,228, which employs sinusoidal gratings in an apparatus and method for testing visual sensitivity of human subjects. The von Gierke and Marko document includes an extensive discussion of the prior art in visual sensitivity measurement including a citation of several publications and patents. The disclosure of the von Gierke and Marko application is also incorporated herein by reference.
Several publications relating to the image array processor used in the preferred embodiment of the invention are listed in the detailed description section below, these references are also considered to be of interest as prior art.